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//                        Kokkos v. 2.0
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#ifndef KOKKOS_UNIQUE_TOKEN_HPP
#define KOKKOS_UNIQUE_TOKEN_HPP

#include <Kokkos_Macros.hpp>

namespace Kokkos { namespace Experimental {

enum class UniqueTokenScope : int
{
  Instance,
  Global
};

/// \brief class to generate unique ids base on the required amount of concurrency
///
/// This object should behave like a ref-counted object, so that when the last
/// instance is destroy resources are free if needed
template <typename ExecutionSpace, UniqueTokenScope = UniqueTokenScope::Instance >
class UniqueToken
{
public:
  using execution_space = ExecutionSpace;
  using size_type       = typename execution_space::size_type;

  /// \brief create object size for concurrency on the given instance
  ///
  /// This object should not be shared between instances
  UniqueToken( execution_space const& = execution_space() );

  /// \brief upper bound for acquired values, i.e. 0 <= value < size()
  KOKKOS_INLINE_FUNCTION
  size_type size() const ;

  /// \brief acquire value such that 0 <= value < size()
  KOKKOS_INLINE_FUNCTION
  size_type acquire() const ;

  /// \brief release a value acquired by generate
  KOKKOS_INLINE_FUNCTION
  void release( size_type ) const ;
};

}} // namespace Kokkos::Experimental

#endif //KOKKOS_UNIQUE_TOKEN_HPP
